Circuit controller



Nov. 12, 1.940.

cIRcUIT-CONTOALLER `Filed Juiys, 1939 `2` sheets-Sheet 1 AHORA/5;?

i Application ruina 1939,

This invention relatesto.communication"sys-` .i

tems and particularlytoitelephone systeifrisAvv-here` in` the speech :channels ere'iused during llulls `in speech and during other intervals whennotbeing l used for speechgfor otherpurposespsuchas .the transmission*offtelegraph signals.

The `object of` theinventionfisf "Q switching which necessarily itime aspeechhannel is converted from ear-telef` a :phone channel to atelegraph ichannel",` `ory vice i ."ver'sa, unnoticeable to afl listener. `Where `such switching is controlled bythe use of` a control tone l whichprecedes speechiythere Vis always ashort interval just beforelthe "speech begins `orijust after u it endswhen the channel is Nin a different` condi` tion. The transition from the normal condition i to said different condition, or vice versapinayl if made suddenly,V as bylthe opening jor'ciosingyof a relaycontact, manifest. itself-to a listener `as Another object of the invention is torender i switching ,operations unnoticeable in a `voice coni trolled circuit in'which the voice is delayed so that a i controiltone may precede themvoice to 25. cause such switching operations." prior Jto the arrival of the voice. f r '1" A feature of i the inventionfismeans ina comi munication system to minimizefthe` `effectof switching operations caused" by voice; operated devices. fw x f i Hereto'fore. switching operations have been carried out by the Ause of the crossed. coil transmission loss unit disclosed in Patent No.`1,'749,85^1,

granted March 11, 1930, to'` H xCwSilentLVIts i use in a systemof the present typeis shownin Patent No. 2,207,720,` granted Julyl, 1940, "to Cole et al. andthe present invention may loeconsidered` an improvement over the Cole et al. inven-V ition.

40` A featurefo'f the present invention" is the `use i of a slow operatingandslow releasingvariable transmission lossi element inza. `voice `frequency i channel under control of acontroljtone transmitted over such channel in response to the action of voice operateddevices at ,the transmit- ,ting end of the channel. This and'otherfeatures will appear pas the description` proceeds. Y l

Another` feature ofthe invention" is the Ause of Va slowoperating channelswitchingfmeansresponsive to `a controlfcurreni..` wherebyx positive action is insured and clipping `of"speecliheretofore an annoying*l feature "of `voiicefcontrolled switchingmeans iseither prevented origreatly reentirely negugime; e j" ducedand its effecten the subscriber is made Telephone Labgmtri showing the detai to render the y takes place! `each Y mitting singin `suppressor'totheihybridcoil lllI NewYork t i (cuna-i c f ih" pres FigQl'Fisa genera Sch' ti whichthe circuitlcotr ent "inventiri, iS D :leadstofahybrida oil n O. tgoingspeechiiead" vizdavlogidiIl` N'Ih ou geingspelh @emphasises through` "a irrism i suppressor 5 and' b means ofj an amplifier; "tector 6 operates achanfofyleiays there labeled asfvoice operated switching circuit." A 1 operated switching circuit controls Matra singing Suppressor: sfoft Roan; pass from Itheftransnu i ithfugh the delay and amplifier v i i i 5 and mi? ":rn

the hybridf coiljl 0 th speech" reach other hybrid coil `lilfand"tlierice geest r"oug the radio 'transmitter *I2 `to an `antenna lff Through radioitransmission mthemspeech will "befrceived fat `someI distantlppoint""andi"fr p,rposes"` ofei-H 25` planation itwill be assunfied that the distant point i vhas 1a receiving circuit ,similar inia1i+re`sberf-to thelower part ofFigmlL"="'I'i1e`speech`-tli`"fore enters antenna 14,!passes )througli*aL radiovr-fv w i ceiverl5 and a .repeater IGto afhybrid; coil |1.^3`0`` From the hybrid coil I1 the zspeechfgoes into i hybrid: coil 18; thence throughfthe receiving singing suppressor* lythe receiving repeater 20,1'a

low-pass filter 2l` andaipathfZZ to a hybridcoil,` Psuch as 2;, iwhenceitjgoes. to the receivingisub- 35 l scriber'over aline, such asfi; 1 i Hilf y VThe receiving-singingfsuppressor l9; is` shown i in detail inrFig. Zand its particular operationwili be described hereinafterw` i f i The voice operated switchingcircuit "ljcontrols 40 a control tone lenabler 23; so that a".sourcefof`` y control'tone; 24 iis `passed throughathe control ,tonellter 25 to thehybridicoil` Hwand th11`s`1ac" .y companies speech.` 1 The voice operated switching circuit 1. also controls a switching `pointleading45 from the receiving switching circuit` 2`6`at ,the i same terminalvtoithe transmitting` suppressor 5" soas to open this circuitduring the periodsspeech Y is going wout: fromfline 1 l; to I antenna; 2131i Durin this time, the `voice 1 operated swiiciiinglpcireui 11150 i also controls the telegraph controlgcircuit H21; t stopthe actionof the telegraphitransrnittingsciri cum i 1 i i i w .At the receiving endg-the jcontroll tone cliliirig` y i in over antenna Mipassesthrough;hybridfcoil yll 55 n and thence vthrough telegraph band elimination `the two printers 42 and 43.

filter 28 and into acontrol tone amplifier and filter 29 and thence into detector 45. This oper-` ates relays CTM and RSS and other relays of the [receiving switching circuit 26. The relay `CTM is known as. the control tone master relay and its .contacts 'foperate througha .-hangover circuit comprising resistances 48, 49 and a condenser 50 to provide a slow release operation; for relay RSS. 'I'he other relays of the receivingy switching circuit perform several functions 'as'V follows.k First, the circuit 26 controlsa normally open circuit between the telegraph band'elirnination filter 28 and the detector l45y including ,a speech amplifier 30. This is provided -so -that when control tone is first received, the receiving switching circuit 26 will be operated thereby and then held operated thereafter by speech currents flowing through the amplifier 38. Y l

The 4receiving switching circuit falso controlsl "the receiving singing` suppressor'il to I4open up the" speechrpath.v The receiving switching circuit 25 also controls' a normally closed path between the band-pass filter 3 I and the telegrad 32` sol that-while speech is being received thetelegrad 32 will vbe disabled. At the'same time, the receiving switching circuit 2 6 controls the switch.-

`ingrelays for two` telegraph channels 33.

During pauses in the speechyeither when the l .subscriber at the distant end is'talking into i: channel I or during the time when the subscriber onchannelv I pauses', during his talk outover the antenna I3, the telegraphapparatus shown in the` upper part of the figure is in operation.

This comprises periorators 34 andA 35 Working lrespectively into tape transmitters 36 and 31 'and thenceintof'rotary distributor 38. `Rotary distributor 38 works through the control circuit 21., which in turnexercises control over the telerkgraphV signal `suppressor 39.

IA source of telegraph signal :tone is supplied byy theiztelegraph signal oscillator.,40 and through the action of `the telegraph signal lsuppressor 39y under the vcntrolfof the control. circuit 21 sends telegraph Ysignals into the hybrid coil IIl, thence through the hybrid coil II and the radio transmitter I2,

and out over the radiofpath from antenna I3.

At the distance end these telegraph signals in the form of Vspurts of alternating current are received over antenna I4 and radio receiver I5 and thence pass through the hybrid coils I1 and I8 to the band-pass filter 3l. Thereafter the signals enter the telegrad 32 and areconverted from varying strength alternating current signals to uniform strength direct current signals of practically the same length at which they were received over the antenna I4. These directeurrent signals then pass through the switching relay'circuit 33 yand the`rotary distributor 4I vto During the reception of telegraph signals the receiving switching circuit'26 is unoperated and the speech path is blocked off by the receiving singing suppressor I9.` f

A line 44 schematically represents the means `for keeping the rotary distributor 38 in exact synchronism with the distantrotary distributor 4I. The rotary distributor 38 and the rotary Vreasons having to do with the cost of synchronizing apparatus, but t froman operating standpoint it is only necessary that the rotary distributors forming part of the same channel be kept in synchronism.

The receiving singing suppressor I9 is a circuit controller and is shown in detail in Fig. 2. The relay'RSS, Vwhich is one of the relays of the receivingl switching circuit operated by the detector 45, is provided with an armature and a front and'aback contact. When the relay is in its idle condition a connection is made from a negative battery through a resistance 5I, the backv lcontact and armature of relay RSS to charge a condenser 52 negatively. This condenser whose other'terininal is grounded, controls the grids lof two .vacuum 'tubes 53 and 54. When the condenser 52 is charged negatively, the vacuum tubes 53 and 54 are conditioned to prevent the flow `of voicecurrents from the in terminals 55 to theout terminals 56. When the relay RSS is operated and the condenser 52 is short-circuited through'the front contact and armature of relay RSS and the resistance 51 to ground, the vacuum tubes 53 and 54 are conditioned to allow free passage of-voicelcurrents from the vin terminals55 to the out terminals 56. 1

- Since the armature of relay -RSS therefore controls a circuit which results in one case in the building up of av charge on condenser 52 and in the othercase in the dissipating of a `charge charging of this condenser takes a nite time,

- theresult will be that the circuit controller opens and closes the speech path from'the hybrid coil I8 to the receiving repeater 20 slowly.

9 This finite time may be'flxed by adjusting the values of thecondenser 52 andthe resistances 5I and 51. By way of example the charge and the discharge of condenser 52 may be made to occur lin Ythirty milliseconds or practically the` time comparable to that rtaken for the envelope of a spoken syllable to reach its crest. c Y

Thus when control tone first comes in over antenna I4 and results in the operationl of relay RSS, thespeech path through the receiving `singingsuppressor vI9 is operated slowly so that the listening subscriber will not be annoyed by the clicks caused by the ysudden change in circuit conditions. Likewise, at the end of a period 'of speech and after the hang-over'period profaffords. In the intervals between received words,

or in brief pauses in speech which are not long enough to cause the listener to take. control of the circuit, the receiving singing suppressor I9 disables the path' to the listener, preventing him :from being ldisturbed by noise or cross-talk.

This'results in a distinct improvement in circuit utilization, permitting the use on traffic of noisy circuits which without the noise suppression would be uncommercial. y

That part of the circuit between and including the radio transmitter I2 and the radio receiver I5 is spoken of asa mutable link since it comprises a signaling.l channel capable of or liable to change fromA internal or external cause which may give rise ito .interfering energy or more specifically, subject4 to noise, fading or change of attenuation. rIt is to be understood, however, kthat the present showingispby way of example and that the term mutable linkldoes not necessarily mean that a. space radio link is in- Aon condenser 52, and since the charging anddisvariably involved but that the term` is broader in its meaningand includes any channel liable to change `from internal or external change.

`What is claimed is:

1. In va communication system, a voice frequency channel including a mutable link, means for normally employing said channel for a iirst type rof communication, switching means `at the transmitting end and at the receiving end of said channel responsive to a second type of communication for halting said first type of communication and conditioning saidy channel for said second type n of communication, said switching `means including at said receiving end a variable impedance device in thecircuit beyond said channel for employment in said second type of communication and means for slowly operating said variable impedance device. l

2. In a communication system, a voice irequency channel including a mutable link. means for normally employing said channel for tele-A graph communication, switching' means atthe transmitting end and at the receiving end of `said channel responsive -to voice currents for halting said telegraph communicationV and for conditioning said channel for telephone communication, Asaid switching means including at said receiving end a variable transmission loss element in a telephone communication circuit and means for slowly operating said variable transmission loss element. Y l

`3. In a communication system, a voice frequency channel including a mutable link, means for normally employing said channel for telegraph communication, switching means at the transmitting ,end and at the receiving endo!` said channel for halting said telegraph` communication and for conditioning said channel for telephone communication, said switching means l at said transmitting end being responsive to voice currents, means also responsive to voice currents for transmitting a control current` `over said channel for operating said switching means `at the receiving end of saidr channel, said switching means at the receiving end oftsaid channel including a variable transmission loss element for rendering the telephone circuits at said receiving end opaque to voice frequency currents during telegraph transmission and transparent to voice frequency currentsv during transmission of said control current and means for slowly and gradually operating said variable transmission loss element. v n

4. In a communication system, a voice i'requency channel including a mutable link, tele-n,

graph circuits and telephone circuits associated with both ends oi said channeLmeans for normally employing said channel for telegraph communication, switching means for disconnecting said telegraph circuits from said channel and connecting in place thereof said telephone lcircuits, voice operated means at the transmitting v `end ofy said channel for operating the said switchlng means thereat, for connecting a source ofl control current tojsaid channel and for delaying the transmission or said voice currents over said l channel, control current operated means at the receiving end oi said channel for operating said switching means thereat including avariable transmission loss element in the telephone cir-` cuit thereail for slowly and gradually changing said telephone circuit from oneopaque tovoice` frequency currents to one transparent to voice frequency currents and vice versa, wherebyhdur` ing the interval between the application oiycon#` trol current to said channel and thebeginning ot transmission of voice currents thereover the ltransition from and to a connection including" said mutable link will be rendered unnotlceable to a listener. 4

`5. Ina communication system. a voice frequency channel including a `mutable link, tele-` l'graph circuits and telephone circuits associated `with both ends of said channel, means `ioiwnorf mally employing said channel for telegraph communication, switching `means for disconnecting the said telegraph circuits from said channel and connecting in place thereof said telephone circuits, voice operated means at the transmitting end of said channel for operating the said switch-` ing means thereat, for `connecting `a source oi control current to saidychannel andior delaying channel, control current operated means at "the receiving end of saidchannel foroperating said i switching means thereatra variable transmission` loss element in the telephone circuit at the re` ceiving end of said channel. a relay operated by" said control current operated meana a condenser connected to said variable loss element for `regulating the loss thereof and charging` and dis" charging circuits for `said` condenserfcontrolled by said relay, said charging and dischargingcircuits being constructed fand arranged toiunc# tion ina time comparable to that takenhfofthe envelope of a spoken syllablev to reach `itscrest.` 6. "In 'a communication system, ayoiceirequency channel including `a mutable link,'*tele l graphcircuits and telephone circuits associated with both ends of said channeh` means, forV normally employing said channel `for telegraphlcommunication, switching means 'for disconnecting i the said telegraph circuitsfrom said channel and connecting in place thereof said `telephonecir- M cuits, voice operated means at thetransmitting i f end of said channel Ioroperating the said switch-7 y ing means thereat, for connecting a source `o control current to said channel and for delaying" 1 j g the transmission of said voice currents overfsaid channel, control current operated means atthe` receiving end of said channel i'or operatingsaid switching means thereat,a variable transmission loss element in the telephone circuit atf thereceiving end of `said channel, a relayv operated by said control current operated means, acondenser` connected to said variable loss elementfor regu-#` as thetransmission of said voice currents over said lating the loss thereof and, charging and` dis-` charging circuits for said condenser controlled` bysaid relay, said charging and discharging cir-ff cuits being constructedand arrangedtoiunction y ina period of the order of thirty milliseconds;` l s. BERGER.

Aus'rnn M. 

